Guide on how to customize you pwm fan curve

incognito · May 15, 2024, 4:35pm

Hmm, the fan control driver should be in the kernel. Did you connect the fan to the proper port?
Also the default curve is just bad, use this one: [Guide] How to make the Rock 5b fan work properly - Joshua Riek's Ubuntu 24.04

Stat_headcrabed · July 9, 2024, 6:26pm

Some additional information:
in property pwms = <&pwm1 0 10000 0>;, the first number is the pwm channel in this device, second number is pwm period(1/pwm frequency), the third number is pwm polarity.

github.com

torvalds/linux/blob/master/Documentation/devicetree/bindings/pwm/pwm.txt

Specifying PWM information for devices
======================================

1) PWM user nodes
-----------------

PWM users should specify a list of PWM devices that they want to use
with a property containing a 'pwm-list':

	pwm-list ::= <single-pwm> [pwm-list]
	single-pwm ::= <pwm-phandle> <pwm-specifier>
	pwm-phandle : phandle to PWM controller node
	pwm-specifier : array of #pwm-cells specifying the given PWM
			(controller specific)

PWM properties should be named "pwms". The exact meaning of each pwms
property must be documented in the device tree binding for each device.
An optional property "pwm-names" may contain a list of strings to label
each of the PWM devices listed in the "pwms" property. If no "pwm-names"
property is given, the name of the user node will be used as fallback.

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beanman109 · September 8, 2024, 2:45am

Do I just need to modify the values in pwm-fan.dts and rerun sudo armbian-add-overlay pwm-fan.dts to change the fan curve once we’ve already set it once?

amazingfate · September 8, 2024, 4:13pm

Yes. Reboot then you will run with new fan curve.

Mathijs · December 27, 2024, 2:50am

Is there a known method to customize the fan curve on the official Radxa image?

bmorton · July 19, 2025, 1:59pm

I have upgrade my Kernel from 5.x to Linux 6.1.115-vendor-rk35xx
now i cannot view the PWM speed anymore:

cat /sys/devices/platform/pwm-fan/hwmon/hwmon8/pwm1
cat: /sys/devices/platform/pwm-fan/hwmon/hwmon8/pwm1: No such file or directory

this worked before it upgraded the kernel.
anyone knows what I am doing wrong?

bmorton · July 19, 2025, 2:15pm

found the solution.
it changed to

cat /sys/class/hwmon/hwmon9/pwm1

incognito · July 19, 2025, 7:27pm

You can do hwmon? for the wildcard to do it for you